Question: What do the following two equations represent? $-5x+4y = -3$ $-20x-25y = 3$
Answer: Putting the first equation in $y = mx + b$ form gives: $-5x+4y = -3$ $4y = 5x-3$ $y = \dfrac{5}{4}x - \dfrac{3}{4}$ Putting the second equation in $y = mx + b$ form gives: $-20x-25y = 3$ $-25y = 20x+3$ $y = -\dfrac{4}{5}x - \dfrac{3}{25}$ The slopes are negative inverses of each other, so the lines are perpendicular.